1. Technical Field
Present exemplary non-limiting embodiments of the technology described herein relate to a line drawing image generating device, a storage medium, and a line drawing image generating method. More particularly, the present exemplary non-limiting embodiments relate to a line drawing image generating device, a storage medium, and a line drawing image generating method for generating line drawing data based on original image data.
2. Description of Background Art
Conventionally, there is a technique for extracting outlines of an original image by performing a predetermined process for original image data (for example, see Japanese Patent Gazette No. 2627744). In a typical outline extracting process, a brightness or color difference between a pixel to be processed and a pixel in a neighboring area (for example, 3×3 pixels) of the pixel to be processed is estimated, and the pixel to be processed is extracted as an outline if the brightness or color difference exceeds a predetermined value. The neighboring area of the pixel to be processed is extended (for example, 5×5 pixels), thereby thickening a width of an outline to be extracted and improving the continuity of the outline.
By the above outline extracting process, line drawing data is generated from arbitrary image data, and a line drawing is displayed on a TV monitor based on the line drawing data. A user may paint the line drawing using a paint program.
Now, in an image used in animation (referred to as an animation cell), an outline of a character is typically black (this black outline is referred to as an ink line), and patterns of the character's clothes and grasses in a background are not especially outlined in black (see FIG. 13). If a conventional outline extracting process is applied to the above image in which the outlines are partially thickened, outlines in a resultant line drawing vary widely in line width. However, a neighboring area of a pixel to be processed, which is referred to when a brightness or color difference is estimated, is extended in order to improve the continuity of the outline of the grasses in the background of the image shown in FIG. 13, for example, the outline of the character is unnecessarily thickened in a resultant line drawing as shown in FIG. 14. As a result, the image becomes artificial, which is a problem.